"The United States is supplicant to the Saudi royal family right now. They reportedly killed a US resident, and they didn't come to us, we went to them," Murphy, a key Democrat on the Senate Foreign Relations Committee, told Business Insider.

'It's hard to understand why the president has put us in such a weak position'

"It's hard to understand why the president has put us in such a weak position with Saudi Arabia and Russia," Murphy said. "It looks today as if they can get whatever they want from the US and this administration, and it raises lots of questions as to why that is."

The senator questioned why Trump is seemingly willing to "sacrifice US national security priorities" to countries with dubious human rights records like Saudi Arabia and Russia. He's not sure the currently Republican-controlled Congress will ever "get to the bottom of that."

"I think it may take Democratic control of at least one chamber to start asking serious questions about why this administration is taking such bizarre positions with both US-Russia policy and US-Saudi policy," Murphy said.

Khashoggi, who was often critical of Saudi leadership in his reporting, went missing on October 2 after entering the Saudi consulate in Istanbul.

Turkish officials have accused the Saudi government of torturing and brutally killing Khashoggi in the consulate. Crown Prince Mohammed bin Salman is believed to have ordered a 15-man team to carry out the hit on Khashoggi.

The Saudis have vehemently denied playing any role in Khashoggi's mysterious disappearance, but after over two weeks have provided no proof he safely departed the consulate.

Despite the damning evidence against the Saudis, Trump has repeatedly touted denials related to the Khashoggi case from the crown prince and his father, King Salman.

Trump has been decidedly reluctant to commit to repercussions against Saudi Arabia, even as a bipartisan group of senators, including Murphy, have called for economic sanctions as well as a cessation of arms sales to the kingdom.

But Trump last week said it would be a "tough pill to swallow" to stop arms sales to the Saudis, and on Wednesday boasted about the billions of dollars of munitions they buy from the US.

'I think the Saudis believe they have a blank check from this presidency'

Murphy has long expressed concern over the US-Saudi relationship, repeatedly urging the US to stop providing Saudi Arabia with arms as it continues to wreak havoc fighting the Iran-backed Houthi rebels in Yemen.

"I think the Saudis believe they have a blank check from this presidency," Murphy told Business Insider. "I don't understand why there's such a close relationship between the Saudi royal family and the Trump family. There may be some business interests that explain the close connect."

Murphy added: "I'm very concerned that US national security policy is for sale and that the business connection between the Saudi royal family and the Trump family may explain why this administration has been so soft on the Saudis throughout the past to years but especially the past week."

'It's a deliberate poke in the eye to their Western allies like the US'

Despite being disconcerted by the Trump administration's approach to the Khashoggi disappearance, Murphy said he remained encouraged by recent condemnation of Saudi Arabia by his colleagues in the Senate, including Republicans.

Murphy said he's hopeful the Khashoggi case will lead more members of Congress "to take stock of a relationship that I think has had much more mixed results for US national security than is the conventional wisdom."

Murphy has zeroed in on the Saudi-led conflict in Yemen, which has led to the deaths of at least 6,500 civilians, including roughly 1,625 children, according to data collected by the UN human rights office. Bombs made and sold by the US have contributed to the slaughter.

"To me what's so indefensible about what's happening in Yemen is that not only are thousands of people dying but the US is participating in the campaign that's killing those people, " Murphy said. "Isn't that much worse than the reported assassination of one journalist?"

'Their record on human rights is getting worse not better'

The Saudis are an important counterterrorism partner, Murphy said, and he's not advocating for the US to completely cut ties. But he thinks the US government needs to hit the reset button on the relationship.

Murphy said the Saudis have become "very militaristic" in terms of their activities in the Middle East in recent years, and that's a particularly point of concern.

"They have continued to export a brand of Islam that often forms the building blocks for groups like Al Qaeda and ISIS," Murphy said. "And their record on human rights is getting worse not better, despite pronouncements from the crown prince that he's committed to modernization."

Murphy thinks the US needs a much more "balanced" relationship with the Saudis in which there isn't such a kneejerk reaction to support "every single one of their plays in the region."